Constructions of this type are used to some extent nowadays.
Beloit Corporation has proposed so-called "FLIP-TOP" frame construction. In this construction, a two-piece intermediate frame is disposed above the press section of the paper machine to connect the front and rear frames of the press section. During the operation of the press section, the ends of the intermediate frame are fixed both to the front and the rear frame. Either of these attachments can be detached and the detached portion of the intermediate frame can be pivoted into the center of the intermediate frame, around the transverse articulated shaft of the paper machine. The partial opening of the intermediate frame has the purpose of facilitating the felt exchange on the press section. The "FLIP-TOP"-frame construction does not essentially improve other functions relating in particular to the service or operability of the press section.
Valmet Oy has proposed several frame constructions of the press section. The so-called SYM-PRESS press section is known, in which horizontal beams providing a solid connection of the front and rear frames of the press section are disposed above the press rolls in a compact press section, both on the service and the driving side of the paper machine. This kind of solution is difficult in particular with regard to the services of the press section, since, being stationary above the press section, the beams hamper and delay the service operations. The further development of this frame construction has resulted in the frame structures described in the Finnish patent applications 844693 and 854959 of Valmet Oy. These publications disclose intermediate frame constructions, in which a one-piece intermediate frame is pivotally articulated to the rear frame of the press section and disposed to be detachably fixed to the front frame (FI-844693), or alternatively, the intermediate frame consists of two pieces, the pieces being articulated into the front frame on the one hand and into the rear frame on the other hand (FI-854959). The free ends of the pieces of the intermediate frame are disposed to be fixed to the fixed intermediate part of the intermediate frame (FI-854959). The intermediate frames described above are pivotable around their articulating points in the vertical plane partly away from above the roll arrangement of the press section especially for service operations. It is difficult to make this type of constructions sufficiently solid and thus resistent to vibration.
The constructor of the press section of a modern paper machine has to fulfill two opposite requirements. On the one hand, the frame construction of the press section, the front frame, the rear frame and the intermediate frame connecting these two, should form a sufficiently rigid construction, which, during the operation of the press section, ensures a trouble-free operation of the press section. However, on the other hand, the compact press section, the machine elements of which, such as press rolls, press fabrics and members for guiding the web, are very close to each other in the operating position, should, in view of the necessary repeated services of the paper machine, have a construction that allows to perform efficiently the service operations. This means that the press section should be opened to a necessary extent relatively easily and the above machine elements should be easily accessible in such opened position.